The SI unit of electric charge is $.........$
Mention the condition under which charges can move in a conductor. Name the device which is used to maintain this condition in an electric circuit.
$(a)$ For the circuit shown in the diagram, calculate
$(i)$ value of current through the $30\, \Omega$ resistor.
$(ii)$ total resistance of the circuit.
$(b)$ Give two advantages of connecting electrical devices in parallel with battery.
A wire connected to a bulb does not glow, whereas the filament of the bulb glows when the same current is passed through them. Why ?
When is potential difference between two points said to be $1$ volt ?